"It seems most local dispensaries are out of it and sell "littles" as a replacement."
Unfortunately there is no one best place I can refer you to. Although commonly found, it varies greatly in quality. Shake is a lose term, but is usually what people call the crumbs that are left over from a bag of cannabis. As the cannabis is moved around, small pieces fall off and accumulate at the the bottom. Some dispensaries will repurpose this, while others will sell it. When you buy shake from dispensaries, they will often mix in ground up trimmings with the shake, so be aware that you may not be getting just crumbs. "Littles" are typically just the smallest buds from the batch of cannabis. They are usually sold at a lower price because they are not as aesthetically pleasing as the rest of the batch. Although often more expensive, the "littles" may be a better value, as they are actual bud as opposed to just the crumbs that fall off. Both shake and littles will come and go as batches of cannabis do, so its tough to direct to one place as a constant source. Keep checking with your local dispensaries. With harvest season coming up, there should be greater availability.